Conventionally, there has been known a waveguide slot array antenna including a combination of plural waveguide subarrays (for example, see Patent Document 1). This type of waveguide slot array antenna is assembled by adhering plural individually-molded waveguide subarrays to each other in the nature of its structure. Therefore, productivity has been extremely poor.
On the other hand, as a method of manufacturing a slot antenna, there is known a technique of integrally connecting a slot plate to a substrate formed with waveguide trenches, by diffusion bonding (for example, see Patent Document 2).    Patent Document 1: Japanese Patent Application Laid-open No. 2000-236213    Patent Document 2: Japanese Patent Application Laid-open No. H10-313214